Veneer for plywood is produced by mounting a log between lathe spindles that turn the log while a lathe blade is controllably moved into the log. A continuous ribbon of thin veneer, e.g. one-tenth of an inch thick, is peeled from the log until the log is reduced to a core diameter too small for peeling.
It is well-known that the log needs to be properly centered in the lathe spindles for optimizing the available veneer in the log. Typically, a centering apparatus is provided at a position spaced from the lathe. The log is centered in the centering apparatus while a previously centered log is being peeled. A transfer device then transfers the log from the centering apparatus to the lathe. This combination of apparatus and method of centering logs, in general, is disclosed in the prior U.S. Pat. No. 4,246,940 issued Jan. 27, 1981.
In such prior apparatus, the centering apparatus typically also involves a geometric centering device, e.g. centering V's that roughly center the log. The log is then gripped by end-pinning spindles similar to but different than the lathe spindles. These end gripping spindles are hereafter referred to as centering or scanning spindles. The centering or scanning spindles rotate the log past stationary scanners. The scanners measure the log at spaced cross sections and convey the measurements to a computer. The computer determines the desired axis of rotation for peeling that log and directs the scanning spindles to adjust the log position so that the desired axis coincides with a replicate axis. The replicate axis is an axis that replicates the lathe axis at a fixed and known position in front of the lathe. The transfer device transports the postitioned log to the lathe spindles so that the prior position of the replicate axis through the log, i.e. the log's desired axis, becomes the turning axis in the lathe spindles.
The present invention is directed to the mechanism that controls the scanning spindles that grip the log, rotates it for scanning, and then adjusts the position of the log in response to computer instructions. The concept of adjustable spindles in general is not new, but the manner by which the apparatus of the present invention accomplishes the adjustment is believed novel and is furthermore believed to be less expensive in construction, has fewer moving parts, and thus less maintenance, and is more accurate and thus more reliable.